1. Field of the Invention
This invention relates to an image forming apparatus which exposes a photosensitive recording medium to a light image such that its size is enlarged, reduced or unchanged, and forms an image on a recording output sheet.
2. Description of Related Art
One well known image forming apparatus which enables image size adjustment comprises a slide printer which enlarges an image recorded in a slide and prints the enlarged image on an output sheet of a predetermined size.
In the slide printer, as shown in FIG. 6, a reflector B is arranged obliquely with respect to a projection direction of a light image from a slide projector A, thereby rendering the printer compact. A photosensitive recording medium comprising a microcapsule sheet C is exposed to the light image reflected by the reflector B. The exposed microcapsule sheet C having a latent image formed thereon is fed to a pressure development part D for pressurizing the microcapsule sheet superposed with an output sheet, a visible image being formed on the output sheet.
In the slide printer, when an output image having a changed size is printed on the output sheets of different sizes, the length of a light path from the slide projector A to the reflector B is changed by moving the slide projector A back and forth. An exposure area on the microcapsule sheet C is thus adjusted thereby.
Because the reflector B is placed at a fixed position in the above-mentioned slide printer, the exposure area on the microcapsule sheet C has a definite extent corresponding to the size of the output sheet, the area being centered on a fixed point. That is, as shown in FIG. 6, if the size of the output sheet is an A4 size, its exposure area is provided within the exposure area of the A3 size and centers on the same point as the center of the exposure area of the A3 size.
When the size of the output sheet is smaller than a maximum size possible to be recorded, (e.g., the output sheet is the A4 size which is smaller than the maximum A3 size) an area from a leading edge (line a-d shown in FIG. 6) of a non-exposure part of the microcapsule sheet C to an edge (line b-c shown in FIG. 6) at which the exposure starts (area enclosed with a,b,c,d in FIG. 6) is fed to the development part D without being exposed, and the microcapsule sheet C is used wastefully.